The therapeutic action of a medicine in a living organism depends to a considerable extent on its formulation. When drugs are administered orally, high demands are made upon the pharmaceutical formulation.
The first demand is a high bioavailability: the medicine in the composition should be made available to the organism in as high an amount as possible and the optimum blood levels should be reached within the shortest possible time.
This is a typical demand in the treatment of infections with an antibiotic composition with which the present invention is concerned.
A second demand made upon pharmaceutical formulations is that it allows administration to the patient without problems. However, the formulation with the best bioavailability is seldom easy to use and on the other hand, one which is easy to use often does not have satisfactory bioavailability.
By way of example: amoxicillin is the most prescribed beta-lactam antibiotic. A considerable amount of amoxicillin is delivered as an aqueous suspension as this shows the best bioavailability. However, such suspensions have serious drawbacks: They have to be prepared by the pharmacist shortly before delivery to the patient. The suspension should be kept cool in a refrigerator because otherwise it is liable to deterioration. When administered it has to be measured with a spoon or a cup with inherent inaccuracy of the dosage volume. Another inconvenience to the patient is the discomfort caused by the sticky sugary liquid and the tacky container.
To overcome these drawbacks other dosage forms, e.g. capsules or tablets, have been made available. However, many patients have serious problems with swallowing such a solid dosage form, especially the larger ones. Moreover the bioavailability and maximum concentration of antibiotic in blood and the time wherein this concentration is reached are inferior to those of the aqueous suspension.
When developing a new pharmaceutical composition, particularly in tablet form, there is still a third category of requirements which has to be met: the ingredients should satisfy the demands of the pharmaceutical production process. Amoxicillin, for example, presents a very bad flow pattern and this, combined with its sensitivity to moisture, places serious restrictions on its formulation. It is also important that the tablet should possess appropriate physico-chemical properties relating to hardness, stability, friability, disintegration time and so on.
To meet these various requirements pharmacy has at its disposal a great variety of adjuvants subdivided as diluents, binders and adhesives, disintegrants, lubricants, glidants and flow promoters as well as colours, flavours and sweeteners. It is the task of pharmacy to develop pharmaceutical formulations which have certain specified properties. One of the common pharmaceutical operations is preparing intimate mixtures of several ingredients. These ingredients may interact with each other during formulation and therefore one cannot predict in detail the physico-chemical characteristics of the resulting pharmaceutical composition which may have surprising properties.